South Korea's new coronavirus cases fell below 4,000 on Sunday as the country has implemented tighter antivirus measures to stem the spike in virus infections and the fast spread of the omicron variant.

The country added 3,833 new COVID-19 infections, including 3,683 local infections, raising the total caseload to 639,083, according to the Korea Disease Control and Prevention Agency (KDCA).

The daily figure marked a decline from 4,875 reported Friday and 4,416 on Saturday.

The fall was largely attributable to less testing over the weekend.

South Korea reported 69 more COVID-19 deaths, raising the total death toll to 5,694.

The number of critically ill COVID-19 patients came to 1,024.

Critical cases have stayed above 1,000 for the 13th consecutive day, with their all-time high hitting 1,151 on Wednesday.

After daily virus cases rose to a record high of 7,848 on Dec. 15, they have slowed down to around 5,000 as the government tightened social distancing rules on Dec. 18 to stem the virus upsurge and the omicron variant.

South Korea's COVID-19 cases spiked after the country relaxed virus curbs in November under the "living with COVID-19" scheme aimed at returning to normal life.

The government has decided to extend antivirus measures for another two weeks starting Monday, including a four-person cap on private gatherings and business hour curfews at cafes and restaurants.

The fast spread of the omicron variant put health authorities on alert. Health experts forecast omicron will become the dominant variant here in one or two months.

The country reported 93 new omicron variant cases, bringing the total to 1,207. Among them, 29 omicron variant cases were imported and 64 locally transmitted.

The accumulated number of omicron infections exceeded 1,000 on Saturday, just one month after the first cases were confirmed on Dec. 1 from travelers returning from overseas.

Of the locally transmitted cases, Seoul reported 1,127, while 1,244 came from the surrounding Gyeonggi Province and 231 from Incheon, 40 kilometers west of Seoul.

The number of cases from overseas came to 150, raising the total to 17,595. (Yonhap)